Butterfly:

Start– The forward start shall be used. Stroke – After the start and after each turn, the swimmer’s shoulders must be at or past the vertical toward the breast. The swimmer is permitted one or more leg kicks, but only one arm pull under the water, which must bring the swimmer to the surface. It shall be permissible for a swimmer to be completely submerged for a distance of 15 meters after the start and after each turn. By that point, the head must have broken the surface of the water. The swimmer must remain on the surface until the next turn or finish. From the beginning of the first arm pull, the body shall be kept on the breast. Both arms must be brought forward over the water and pulled back simultaneously.

Kick– All up and down movements of the legs and feet must be simultaneous. The position of the legs or the feet need not be on the same level, but they shall not alternate in relation to each other. A scissors or breaststroke kicking movement is not permitted.

Turns– At each turn the body shall be on the breast. The touch shall be made with both hands simultaneously at, above or below the water surface. Once a touch has been made, the swimmer may turn in any manner desired. The shoulders must be at or past the vertical toward the breast when the swimmer leaves the wall.

Finish– At the finish the body shall be on the breast and the touch shall be made with both hands simultaneously, at, above, or below the water surface.